Method for producing sandwich components

Abstract

The invention relates to a sandwich component composed of at least two building material plates which are arranged essentially parallel to one another at a distance from one another and have a polyurethane foam core between the spaced building material plates, wherein the ratio of the greatest measured compressive modulus of the polyurethane foam core in a direction oriented parallel to the building material plates to the compressive modulus of the polyurethane foam core in a direction oriented perpendicular to the building material plates is less than 1.7. To produce the sandwich components, a mixture of (a) at least one polyisocyanate component, (b) at least one component which comprises at least one polyfunctional compound which is reactive toward isocyanates and (c) at least one blowing agent is introduced by the high-pressure injection method into a hollow space between spaced building material plates. The process makes it possible to produce sandwich components whose foam core has reduced anisotropy combined with good insulation values.

1 . A sandwich component comprising at least two building material plates which are arranged essentially parallel to one another at a distance from one another and have a polyurethane foam core between the spaced building material plates, wherein the ratio of the greatest measured compressive modulus of the polyurethane foam core in a direction oriented parallel to the building material plates to the compressive modulus of the polyurethane foam core in a direction oriented perpendicular to the building material plates is less than 1.7. 
     
     
         2 . The sandwich component according to  claim 1 , wherein the core density of the polyurethane foam core is in the range from 20 to 100 kg/m 3 . 
     
     
         3 . The sandwich component according to  claim 1 , wherein at least one of the building material plates is provided at least partly with a primer on the side facing the polyurethane foam core. 
     
     
         4 . The sandwich component according to  claim 1 , wherein the building material plates are made of concrete, geopolymers or gypsum plaster. 
     
     
         5 . The sandwich component according to  claim 1 , wherein the fresh foam of the sandwich component has a thermal conductivity in the range from 16 to 30 mW/m·K. 
     
     
         6 . A process for producing sandwich components comprising at least two building material plates which are at a distance from one another and have a polyurethane foam core, comprising the following steps:
 A) mixing of (a) at least one polyisocyanate component, (b) at least one component which comprises at least one polyfunctional compound which is reactive toward isocyanates and (c) at least one blowing agent by the high-pressure injection process to form a mixture; and   B) introducing the mixture obtained into a hollow space between the spaced building material plates, where the compaction of the foam is in the range from 1.1 to 2.5, where the compaction is the ratio of the density of the foam in the hollow space divided by the density of the free-foamed foam body.   
     
     
         7 . The process according to  claim 6 , wherein the mixing of the components (a) to (c) is carried out in a mixing chamber at a pressure of at least 100 bar. 
     
     
         8 . The process according to  claim 6 , wherein the blowing agent is selected from C 3 -C 5 -alkanes, C 4 -C 6 -cycloalkanes, di-C 1 -C 4 -alkyl ethers, methyl formate, formic acid, acetone, fluorohydrocarbons, partially halogenated fluoroolefins, chlorofluorocarbons, carbon dioxide, water and mixtures of two or more thereof. 
     
     
         9 . The process according to  claim 6 , wherein at least one catalyst for the reaction of the polyisocyanate component with the polyol component is added in step A). 
     
     
         10 . The process according to  claim 6 , wherein the amount of the mixture introduced into the hollow space in step B) is such that the overall injected foam density is less than 100 kg/m 3 , where the overall injected foam density is the total amount of mixture from step A) which is introduced divided by the total volume of the hollow space to be filled with foam. 
     
     
         11 . The process according to  claim 6 , wherein the amount of mixture introduced into the hollow space in step B) is in the range from 0.1 to 8 kg/s. 
     
     
         12 . The process according to  claim 6 , wherein at least one of the building material plates is provided at least partly with a primer on the side facing the hollow space. 
     
     
         13 . The process according to  claim 12 , wherein the primer is based on a physically setting binder and/or a chemically curing binder. 
     
     
         14 . The process according to  claim 13 , wherein the primer is based on a binder selected from among an epoxy resin, post-crosslinking acrylate dispersions or post-crosslinking alkyd resin dispersions. 
     
     
         15 . The process according to  claim 12 , wherein the primer is applied in an amount in the range from 20 to 600 g/m 2 . 
     
     
         16 . The process according to  claim 6 , wherein the building material plates are made of concrete, geopolymers or gypsum plaster. 
     
     
         17 . The sandwich component according to  claim 1 , wherein the fresh foam of the sandwich component has a thermal conductivity in the range from 22 to 28 mW/m·K. 
     
     
         18 . The process according to  claim 6 , wherein the mixing of the components (a) to (c) is carried out in a mixing chamber at a pressure in the range from 100 bar to 300 bar. 
     
     
         19 . The process according to  claim 6 , wherein the amount of the mixture introduced into the hollow space in step B) is such that the overall injected foam density is less than 80 kg/m 3 .